1. Field of the Invention
The present invention relates to a biopsy apparatus for identifying a lesion position based on a tomosynthesis image and extracting a piece of tissue from the lesion position, and an operation method of the biopsy apparatus.
2. Description Related to the Prior Art
A biopsy apparatus intended for extracting a piece of tissue from a lesion (tumor or calcification) of a patient and conducting a detailed examination for medical diagnosis has been developed. The biopsy apparatus inserts a hollow biopsy needle into a subject to be examined (breast or the like) of a patient, so as to extract a piece of tissue which enters into the biopsy needle.
As the biopsy apparatus, there is a stereotactic biopsy apparatus, in which stereotactic imaging is performed on a subject to be examined by using radiation, so as to obtain two radiographic images (i.e., stereotactic image) and identify a three-dimensional position of the lesion with use of the obtained two radiographic images, and then a biopsy needle is moved based on the identified position.
Specifically, in the stereotactic biopsy apparatus, a tube of a radiation source is moved to two positions each having a different angle relative to the subject to be examined (i.e., stereotactic tube positions), and radiation is irradiated from the tube at each of the stereotactic tube positions. Then, an image of the radiation having passed through the subject to be examined is captured by a radiation detector, and thus each of the radiographic images constituting the stereotactic image is generated. The stereotactic image is displayed on a monitor. A user such as a doctor designates a lesion position as a target, into which the biopsy needle is to be inserted, in each of the radiographic images. Three-dimensional position information of the designated lesion position is calculated based on the stereotactic image, and the biopsy needle is moved in accordance with the calculated lesion position.
The stereotactic biopsy apparatus recognizes each of the lesion position and the position at which the biopsy needle is to be inserted as a position in a three-dimensional coordinate system, and controls movement of the biopsy needle. Accordingly, a biopsy coordinate system for use in the control of the movement of the biopsy needle and a stereotactic coordinate system for use in the stereotactic imaging for recognizing the lesion position should be coincident with each other exactly. In order to ensure that the biopsy coordinate system and the stereotactic coordinate system are coincident with each other, in principal, it is sufficient to design a movement mechanism of the tube and the biopsy needle and the like with a high degree of accuracy and perform positioning by mechanical adjustment, so as to avoid deviation between the biopsy coordinate system and the stereotactic coordinate system.
However, since the degree of deviation practically acceptable is as small as at most about 1 mm, it is difficult to achieve the acceptable degree of accuracy by the mechanical adjustment of the movement mechanism of the tube and the biopsy needle and the like. Therefore, calibration between the biopsy coordinate system and the stereotactic coordinate system is performed before using the biopsy apparatus, so as to acquire calibration data for associating the biopsy coordinate system with the stereotactic coordinate system (see Japanese Patent Laid-Open Publication No. 2010-75316). In order to control the movement of the biopsy needle, the lesion position identified in the stereotactic coordinate system is converted into a corresponding position in the biopsy coordinate system, and the movement of the biopsy needle is controlled based on the corresponding position obtained by the conversion.
Further, recently, tomosynthesis imaging has been known. In the tomosynthesis imaging, the tube of the radiation source is moved to capture an image of the subject to be examined of a patient from a plurality of directions, and a plurality of tomographic images are reconstructed from a plurality of radiographic images obtained by the image capturing (i.e., projection images) by image processing. The plurality of tomographic images are referred to as a tomosynthesis image, and have three-dimensional information of the subject to be examined. The tomosynthesis image is a high-definition three-dimensional image making it easier to confirm the lesion at which tissues are overlapped with each other, and used as a clinical diagnostic image.
A tomosynthesis biopsy apparatus obtained by adding the tomosynthesis imaging function to the biopsy apparatus, which is capable of designating the lesion position (target) based on the tomosynthesis image, has been known (see United States Patent Application Publication No. 2014/0073913 corresponding to Published Japanese translation of PCT application No. 2009-526618). It is necessary to designate the lesion position in each of the radiographic images constituting the stereotactic image in the stereotactic biopsy apparatus. In contrast, the tomosynthesis biopsy apparatus has an advantage in that three-dimensional position information of the lesion position can be acquired by finding the tomographic image in which the lesion appears from the tomosynthesis image and designating the lesion position in the tomographic image only once. Further, there is a lesion which is not visible in the stereotactic image but which is visible in the tomosynthesis image, and therefore the tomosynthesis biopsy apparatus also has an advantage in that such a lesion can be subjected to the biopsy.
Additionally, a biopsy apparatus obtained by adding the tomosynthesis imaging function to the stereotactic biopsy apparatus, which is capable of performing both the tomosynthesis imaging and the stereotactic imaging, has been known (see Japanese Patent Laid-Open Publication No. 2012-245329).
As disclosed in Japanese Patent Laid-Open Publication No. 2010-75316, calibration between the stereotactic coordinate system and the biopsy coordinate system is normally performed in the stereotactic biopsy apparatus, and calibration data for associating the stereotactic coordinate system with the biopsy coordinate system is acquired.
In the case where the tomosynthesis imaging function is added to the stereotactic biopsy apparatus and the target is designated based on the tomosynthesis image as disclosed in Japanese Patent Laid-Open Publication No. 2012-245329, it is necessary to associate the tomosynthesis coordinate system with the biopsy coordinate system.
In the tomosynthesis imaging, the tube of the radiation source is set to a lot of positions for the purpose of the image capturing. An error in setting each of the positions of the tube results in deviation of the tomosynthesis coordinate system. Therefore, it is perceived that the amount of deviation of the tomosynthesis coordinate system from the biopsy coordinate system is larger than the amount of deviation of the stereotactic coordinate system from the biopsy coordinate system.
Accordingly, in the case where the target is designated based on the tomosynthesis image, it is necessary to perform calibration between the coordinate systems with a higher degree of accuracy in comparison with the case where the target is designated based on the stereotactic image.
However, in order to perform calibration for associating the tomosynthesis coordinate system with the biopsy coordinate system, it is necessary to create calibration data by a procedure in which a calibration biopsy needle, for example, is driven to perform the tomosynthesis imaging, and position information of a tip portion of the calibration biopsy needle in the biopsy coordinate system is compared with position information of a tip portion of the calibration biopsy needle obtained by the tomosynthesis imaging, as disclosed in Japanese Patent Laid-Open Publication No. 2010-75316. As described above, the calibration between the tomosynthesis coordinate system and the biopsy coordinate system with a high degree of accuracy is troublesome and a burden to a user. Further, in the case where the calibration between the tomosynthesis coordinate system and the biopsy coordinate system is not performed, although the lesion position in the subject to be examined can be identified with a high degree of accuracy by the tomosynthesis imaging, deviation between the lesion position and the position into which the biopsy needle is inserted may occur.